Node Type peer-peer issue

On a windows 2000 server, suddenly, I found in ipconfig the node type moved
in peer-peer. Obviously, the server sharing are impossible to be reach
surfing the network, and from this server is impossible to find any network
object.
This a stand-by server in a cluster configuration. I tried to add the regedit
key Nodetype "8" (hybrid, in
HLM\SYSTEM\CurrentControlSet\Services\NetBT\Parameters), with no result;
and, at the same time, Oracle on the cluster crashed. Now the Oracle is ok,
but the security in my cluster is very low. Someone has any idea about this
issue?
Many thanks,
Marco Riccardi